Electrical ignitor for fuel ignition

ABSTRACT

An electrical ignitor for fuel appliances formed of a mounting block of insulating material having an opening therein. An ignitor element having fragile properties is exposed to the opening in the mounting block. A pair of buss terminals are rigidly secured at one end to the mounting block and the ignitor element is mounted between the other ends of the buss terminals. The ends of the buss terminals to which said ignitor element is mounted can expand and contract with temperature changes so as to prevent the ignitor element from breaking. The ignitor element may be formed of molybdenum disilicide which is soldered or otherwise attached to the buss terminals.

United States Patent 1 1 3,569,787

[72] Inventor ReedA.Palmer 1,393,888 10/1921 Farnsworth 219/270 Glendale,Calil. 2,912,623 11/1959 317/79 21 Appl.No. 795,815 2,993,977 7/1961 219/270 22 Filed Feb.3,l969 3,017,540 1/1962 317/98 45 Patented Mar.9,197l 3,139,558 6/1964 317/98 [73] Assignee International Telephone and Telegraph 3,419,705 12/1968 219/270 g g g z Y FOREIGN PATENTS 334,522 3/1921 Germany 338/316 729,359 12/1942 Germany 219/270 [54] ELECTRICAL IGNITOR FOR FUEL IGNITION 1 Claim, 4 Drawing Figs.

s2 u.s.c1 317/98, 219/223, 219/270, 219/552, 338/316,431/262 51 int. Cl F23g7/24 [50] Field of Search 219/260- e 3, 276- 8, 270, 541, 264/552-3; 317/98, 79;

Primary Examiner-Bernard A. Gilheany Att0rneysC. Cornell Remsen, Jr, Walter J. Baum, Paul W.

l-lemminger, Percy P. Lantzy and Thomas E. Kristofi'erson ABSTRACT: An electrical ignitor for fuel appliances formed of a mounting block of insulating material having an opening therein. An ignitor element having fragile properties is exposed to the opening in the mounting block. A pair of buss terminals are rigidly secured at one end to the mounting block and the ignitor element is mounted between the other ends of the buss terminals. The ends of the buss terminals to which said ignitor element is mounted can expand and contract with temperature changes so as to prevent the ignitor element from breaking. The ignitor element may be formed of molybdenum disilicide which is soldered or otherwise attached to the buss terminals.

PATENTED m 9 1971 INVENTQR. BY REED A. PALMER H M AT ORNEY ELECTRICAL IGNITOR FOR FUEL IGNITION ELECTRICAL IGNITOR FOR FUEL IGNITION The invention relates in general to an electrical ignitor for use in fuel appliances and, more particularly, to a mounting means for an ignitor element having very fragile properties.

BACKGROUND OF THE INVENTION Increased use of fuel appliances by consumers has been a direct result of automatic ignition devices. The most popular of these devices has been the pilot light" which requires a continuous combustion of a small amount of fuel. Such combustion produces a continuous undesirable heat. Further, should the pilot light be extinguished, complex arrangements are necessary to rekindle the pilot light. Moreover, safety devices are required so that should the pilot light become extinguished, the source of fuel to the pilot is automatically turned off. I

An approach to eliminating use of pilot lights in fuel appliances has been the use of high tension spark ignitors. Such a device has met with consumer resistance due to the noise produced by the ignitor. Further, the source of the high tension spark must be in a relatively cool spot causing installation problems in many appliances. Another approach to fuel appliance ignition has been the use of piezoelectric ignitors. However, these devices are very heat sensitive and do not function at high ambient temperatures. Therefore, once the appliance has been turned on, heat from the appliance is transmitted to the piezoelectric device, rendering it inoperative until the device cools down sufficiently.

Still another approach to ignition of fuel has been the use of electrical ignitors such as the generating of an electrical current through a platinum wire. For example, the current through the platinum wire heats the wire in the presence of natural gas and when the platinum reaches approximately 2100 F., ignition of the gas occurs. The major drawbacks to platinum wire ignitors has been its prohibitive expense coupled with a relatively short life at temperatures required for fuel ignition.

A recent development in the field of electrical ignition has been the suggestion of the use of molybdenum disilicide, sold under the name of Kanthal. While Kanthal has for many years been made into heating elements from large gauge extruded molybdenum disilicide, it is only recently that Kanthal has been made sufficiently thin so thatreasonable amounts of power would be required to heat the Kanthal to the temperature required for ignition of fuel. Theprime drawback to the use of Kanthal is that when it is made sufficiently thin so that reasonable amounts of power are required to ignite the fuel, the Kanthal is extremely fragile, having breaking properties closely akin to hard pencil lead.

In order to overcome the attendant disadvantage of prior art fuel ignitors, the present invention utilizes molybdenum disilicide wire which is sufficiently thin so that a minimum of power is required to ignite the fuel with the wire. The wire is mounted so that damage to the wire is minimized. Further, the wire is packaged so as to prevent user contact while cleaning the appliance. Moreover, an improved junction means is provided between the wire and its associated terminals.

SUMMARY or THE INVENTION More particularly, the invention comprises an electrical ignitor for fuel appliances formed of 'a mounting block of insulating material having an opening therein. An ignitor element having fragile properties is exposed to the opening in the mounting block. A pair of buss terminals are rigidly secured at element may be formed of molybdenum disilicide which is soldered, or otherwise attached to the bus terminals in an electrically and thermally conductive manner. I

The advantage of this invention, both as to its construction and mode of operation, will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the FIGS.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a perspective view of the electrical ignitor in accordance with the invention, disassembled;

FIG. 2 is a top view of the electrical ignitor of FIG. 1;

FIG. 3 is an exploded perspective view of a portion of the ignitor illustrating some subassembly steps; and

FIG. 4 is the perspective view of a portion of the ignitor illustrating a succeedings subassembly step.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown a preferred embodiment of the electrical ignitor 12 in accordance with the invention. The ignitor comprises. a base member having an upper portion 14 and a lower portion 16. The portions 14, 16 may be identical and formed of an insulating ceramic substance such as alumina. A riveting hole 18 is formed in the center of base for securing the upper portion to the lower por tion.

Secured between'the portions 14, 16 are a pair of identical terminals 22, 24 for connection to a source of electrical current. Each of the terminals are L-shaped and have a leg portion 26 for connection to an electrical source and a side portion 28.

A pair of buss members 32, 34 are connected to the L- shaped terminals 22, 24, respectively. Each of the buss members 32, 34 comprise an end section 36 which is spot welded to the leg portion 26 at its junction with the side portion 28. Further, a mounting section 38 of the buss members is offset from the end section by means of an intermediate section 42. The mounting section may further contain a plurality of holes 44 for improving its flexibility. An inwardly facing pocket 46 is formed at the end of the mounting sections. A measured length of high heat resistant fusible metal brazing wire is spot welded to the outer end of the inwardly facing pocket The base member has a pair of slots 48, 52 in each of the portions 14, 16 into which a portion of the terminals 22, 24 and the buss members 32, 34 are secured. The slots 48, 52 are formed in a raised ridge area 54 at one end of the upper portion 14 and the lower portion 16. Further, a second ridge area 56 is formed at the other end of the portions 14, 16 adjacent large ignition opening 58in the base member.

The portions of the terminals 22, 24 and buss members 32, 34 which are mounted in the slots 48, 52 and the ridge areas 54, 56 are secured by means of a ceramic cement. The ceramic cement allows the terminals 22, 24 and buss members 32, 34 which are normally made of stainless steel, to be rigidly fixed to the base member in the slots, while simultaneously, the mounting sections 38 which are exposed between the ridge areas 54, 56 remains flexible. Further, a rivet 60 in the hole 18 secures the portions 14, 16 together. Alternatively, holes may be formed in the portions 14, 16 so that the ceramic cement may be injected after assembly of the device.

After the terminals 22, 24, buss members 32, 34, and portions l4, 16 have been secured to each other, a piece of molybdenum disilicide wire element 62 is placed across the pockets 46 so that the wire is exposed in the ignition opening 58. Then the entire device is fired in an oven until the element 62 is fused to the wire in the pockets. Excessive amounts of the fusible metal wire can cause reduction in the effective length of the element should the metal cover the element 62 upon heating, the covered portion of the element being shunted by the fusible metal wire.

By mounting the ignitor element 62 between the insulating portion 14, 16 and soldering the element 62 to the buss terminals 32, 34 at pockets 46, it has been found that an improved junction results. Further, damage caused by movement and temperature changes to the ignitor element is minimized. Moreover, contact with the ignitor element during cleaning of the appliance is minimized.

As an example, utilizing an ignitor element of molybdenum disilicide having a diameter of 0.016 inches and a length of five-eighths inch, l /22 seconds were required to raise the wire to 2400 F. (ignition temperature of natural gas in the presence of molybdenum disilicide), with a 1.8 volt source and a current of 4.7 amperes. Units of this type were tested 75,000 times without failure to the wire.

Referring now to FIGS. 3 and 4, there is shown an altemative embodiment for mounting the wire element 62 in a buss member. In FIG. 3 the buss members 72, 74 each contain an aperture 76,78, respectively, through which the ignitor element 62 passes. On the outer surface side of the buss members 72, 74, a metal bushing 84 which may be made of stainless steel, is fitted around the wire element 62. The edge surface of the bushing is normally spot welded to their respective buss members and then the bushing is plasma-arc welded to the ignitor element 18, forming a seal as shown in FIG. 4. The embodiment depicted in FIGS. 3 and 4 prevents corrosion of the buss members by the brazing material which could occur in the embodiment of FIG. 1 and 2. Further, the embodiment of FIG. 3 and 4 is not as affected by the high ambient temperatures which would melt or oxidize the brazing materials.

I claim:

1. An electrical ignitor for fuel appliances comprising:

a mounting block of insulating material having an opening therein;

an ignitor element having a rod-shaped structure and having fragile properties exposed to said opening in said mounting block;

means for securing said ignitor element within said block comprising a pair of bus terminals;

said buss terminals being rigidly secured at one end to said mounting block and having said ignitor element mounted between its outer ends for allowing said other ends to expand and contract with temperature changes, thereby preventing said ignitor element from breaking;

said mounting block comprising an upper portion and a lower portion, said buss terminals being secured between said mounting block portions;

said mounting block portions having slots therein for inserting said buss terminals; and

said buss terminals having apertures through which the ends of said ignitor element extends, a metal bushing surrounding said ignitor element ends, said ignitor element and said metal bushings being welded together. 

1. An electrical ignitor for fuel appliances comprising: a mounting block of insulating material having an opening therein; an ignitor element having a rod-shaped structure and having fragile properties exposed to said opening in said mounting block; means for securing said ignitor element within said block comprising a pair of buss terminals; said buss terminals being rigidly secured at one end to said mounting block and having said ignitor element mounted between its outer ends for allowing said other ends to expand and contract with temperature changes, thereby preveNting said ignitor element from breaking; said mounting block comprising an upper portion and a lower portion, said buss terminals being secured between said mounting block portions; said mounting block portions having slots therein for inserting said buss terminals; and said buss terminals having apertures through which the ends of said ignitor element extends, a metal bushing surrounding said ignitor element ends, said ignitor element and said metal bushings being welded together. 